Fusor Forums

I was able to test the power supply I've been designing/building at the full voltage/power rating today on my fusor.

Here is a picture of the preliminary setup (the multiplier has a built-in voltage divider and current sense):
At the moment, I'm running "open loop" with the half-bridge inverter I designed and the feedback is read by two multimeters, but in the near future this will be a fully regulated (cc/cv) system.

I ran a number of tests today at -180kV and 7mA! The neutron levels continued to increase significantly from my 125kV max runs.

Some details:
10-Stage Full-Wave Multiplier Submerged in Dielectric Oil
50kHz ac supplied by two 180deg out of phase transformers (21:1000 ratio)
2.5 Gohm Voltage Divider, and Bottom Side Current Sense

Impressive work Joe
I’m totally convinced multiplier circuitry is the future of fusor power supplies.

Mark arowley

It seems the ions really are predominately D2+. With 180kV applied, the ions have the equivalent velocity as D+ at 90kV, therefore it makes sense why I'm still seeing significant gains. I'm really glad I took the time to reinforce my neutron/X-ray shielding. (On another note, I ran with helium and saw virtually no neutron counts from X-Rays).

It is hard to imagine any significant number of intact molecules of D2 surviving in the confines of the high velocity maelstrom of 100kv differential fields in a cube fusor. The electrons in the mix would see to destroying the very weak molecular bonds, I would think. The mean free path in a small cube would exceed the dimensions of the device for both ions and electrons. Most all fast neutrals and virtually 100% of the electrons wind up at the walls. As the cylinder grids are a form of BOT in a cube, I guess the bulk of the volume could be really cool compared to a complex geodesic in a spherical reactor with many beams.

Richard Hull

The pressure is quite high and there are probably quite a few collisions that are causing molecular recombination. At the very least there is significant velocity distribution among ions.

A thing of beauty!

It will be interesting how to compensate feedback of the supply so that it doesn't oscillate with a load as unruly and non-linear as the fusor.

Great work as always!

So running some numbers based on your post (((180,000 / 10) / 1000) * 21) / 1.414 = 267V RMS.

Are you running that beast off a single tap from a 480KV 3 phase line? That would be a nominal RMS voltage of 277V relative to neutral/ground.

I'm just wondering how you are getting your line voltage of ~270V.

Joe.

@Joe

It's a resonant converter, so you get a boost greater than the turns ratio ... and the front end is a PFC boost stage for the DC bus feeding the half-bridge.

@Cai

It's certainly doable. Everyone who uses a Spellman or Glassman supply to run a fusor has experienced this first hand. I plan on using type-III compensation.

Here is my control board (there is a separate board for the Boost Stage and Half-Bridge Inverter)